The invention relates to a combined service brake and spring brake cylinder for brake systems of vehicles.
A generic combined service brake and spring brake cylinder is known for example from DE 40 11 739 A1, wherein the bayonet coupling between the spring brake cylinder and the intermediate wall comprises a separate bayonet ring which, by way of its radially inwardly pointing bayonet segments, engages over both locking elements of the spring brake cylinder and also locking segments of the intermediate wall. Here, an annular seal is arranged between the radially inner circumferential surface of the end-side edge, which has the locking elements, of the spring brake cylinder and a radially inner circumferential surface of the annular chamber, which annular seal seals off the pressure chamber, which can be aerated and deaerated, with respect to the environment. In this case, the annular seal is held in a groove on the radially inner circumferential surface of the annular chamber.
By contrast, it is the object of the invention to further develop a combined service brake and spring brake cylinder of the type mentioned in the introduction such that it ensures improved sealing of the pressure chamber of the spring brake cylinder.
The object is achieved by providing A combined service brake and spring brake cylinder (1) for brake systems of vehicles, in particular utility vehicles, having                a) a service brake piston or service brake diaphragm which is arranged in the service brake cylinder and which can be actuated by a pressure medium and which is operatively connected to a service brake piston rod, the latter projecting out of the service brake cylinder and acting on brake actuation elements,        b) a spring brake piston which is arranged in the spring brake cylinder and which can be actuated by an accumulator spring and which is delimited on one side by a pressure chamber and on the opposite side by a spring chamber that accommodates the accumulator spring, wherein the accumulator spring is supported at one side on the spring brake piston and at the other side on the base of the spring brake cylinder,        c) an intermediate wall between the service brake cylinder and the spring brake cylinder, which intermediate wall is extended through by a spring brake piston rod which is connected to the spring brake piston,        d) a bayonet coupling between the spring brake cylinder and the intermediate wall, which bayonet coupling has, on an end-side edge of the wall of the spring brake cylinder, radially outwardly projecting locking elements and radially inwardly molded recess segments and has, formed correspondingly to these on an annular chamber which is connected to the intermediate wall, radially outwardly molded recess segments and locking segments which project radially inward into the annular chamber,        e) a base-side abutment surface in the annular chamber as an axial abutment for the end-side edge of the wall of the spring brake cylinder,        f) an annular seal which is arranged between the radially inwardly pointing circumferential surface of the edge of the wall of the spring brake cylinder and the radially outwardly pointing circumferential surface of the annular chamber, characterized in that        g) a recess is provided in the base of the annular chamber for the purpose of receiving at least one end section of the annular seal, and        h) face-side contact surfaces are provided on the locking segments of the spring brake cylinder for the purpose of abutting against the base-side abutment surface in the annular chamber, wherein        i) at least the end section of the annular seal is clamped between the recess in the base of the annular chamber and the edge of the wall of the spring brake cylinder.        
The object is also achieved by providing a method for producing a combined service brake and spring brake cylinder of said type.
It is proposed that a recess be provided in the base of the annular chamber for the purpose of receiving at least one end section of the annular seal, and that face-side contact surfaces be provided on the locking segments of the spring brake cylinder for the purpose of abutting against the base-side abutment surface in the annular chamber, wherein at least the end section of the annular seal is clamped between the recess in the base of the annular chamber and the edge of the wall of the spring brake cylinder.
The method for producing the combined service brake and spring brake cylinder then comprises at least the following steps:                a) positioning the annular seal on the radially inwardly pointing circumferential surface of the annular chamber and positioning the end section of the annular seal in the recess in the base of the annular chamber,        b) inserting the end-side edge of the wall of the spring brake cylinder by translational movement into the annular chamber of the intermediate wall, with the locking segments being inserted into the corresponding recess segments, until the face-side contact surfaces of the locking segments of the spring brake cylinder come into contact with the associated base-side abutment surface of the annular chamber, with at least the end section of the annular seal being clamped between the recess in the base of the annular chamber and the end-side edge of the wall of the spring brake cylinder,        c) rotating the spring brake cylinder and intermediate wall relative to one another such that the radially outwardly projecting locking elements of the spring brake cylinder engage in positively locking fashion behind the radially inwardly projecting locking elements of the intermediate wall within the annular chamber.        
The recess in the base of the annular chamber permits centering of the annular seal in a defined position before the spring brake cylinder and intermediate wall are joined together. Said centering assists in achieving that the annular seal is not displaced out of its defined position as a result of the translational insertion of the edge of the wall of the spring brake cylinder during the locking of the bayonet coupling.
Furthermore, the abutment of the face-side contact surfaces on the locking segments of the spring brake cylinder against the abutment surface on the base of the annular chamber assists in achieving that the annular seal is not squeezed to an excessive extent, and thus damaged, during the translational insertion of the edge of the wall of the spring brake cylinder. A defined available space for the end section of the annular seal is thus predefined.
It is not least the case that the clamping of the annular seal defined by contact surfaces and abutment surface ensures a certain degree of compression of the annular seal, and thus improved sealing behavior.
It is particularly preferable if the contact surfaces of the locking segments of the spring brake cylinder extend over the entire segment arc and, being formed as axial recesses in a face surface of the edge of the wall of the spring brake cylinder, have a spacing of 0.1 to 0.3 mm from said face surface. Said recesses, which are of small dimensions in the axial direction and on which the contact surfaces are formed, prevent the edge of the wall from protruding to an excessively great extent into the annular chamber and thus prevent excessive clamping of and damage to the annular seal.
It is furthermore preferable if the contact surfaces of the locking segments of the spring brake cylinder, measured with a spacing of 2.1 mm to 2.3 mm from the radially inwardly pointing circumferential surface of the edge of the wall of the spring brake cylinder, extend to the radially outwardly pointing circumferential surface of the locking segments.
It is preferable here if the base-side abutment surface in the annular chamber for the contact surfaces of the locking segments of the spring brake cylinder is arranged radially to the outside of the recess in the base of the annular chamber for the annular seal.
It is particularly preferable if the annular chamber is formed integrally with the intermediate wall. It is then possible to dispense with the production of a bayonet ring as in DE 40 11 739 A1, which simplifies the production of the combined service brake and spring brake cylinder.
In one refinement, the annular seal is of bone-like form in cross section, with end sections of bead-like form and with a central section narrowed in relation to said end sections. The other end section of the annular seal is then clamped elastically in the radial direction between a radially inwardly pointing circumferential surface of the edge of the wall of the spring brake cylinder and a radially outwardly pointing circumferential surface of the annular chamber of the intermediate wall. This ensures a sealing action and a force fit which prevents release of the bayonet coupling.